Diameter of Axle Rods(mm)See comments *2 (Screwed Rods or Bolts are used as axles.)

Types of Nuts and BoltsNuts: hexagonalBolts: fillister (slotted)

Material/Finish of Nuts and BoltsSteel with a Steel finish(see comment *3)

Size of the Nuts across Flats (mm)7

Bolt diameter (mm)

CommentsThe one set seen, on Ebay, has Strips, Angle Girders, Pulleys, & parts to make cars for a Big Wheel etc. Said cars used in the Big Wheel on the lid & a Roundabout ride in the manual. *1 13.8-13.9. *2 Only Crank Handle. *3 plain aluminium Nut.

Below there are manuals/leafets and photos which can be downloaded by clicking on the appropriate image.

A Der Kleine Ingenieur(4) manual(Scans from Urs Flammer)

A Der Kleine Ingenieur(4) model sheet(Scans from Urs Flammer)

Various photos of the Der Kleine Ingenieur(4) construction system(Scans from Urs Flammer)